How to remove previous owner iCloud from intel-based Mac with T2 remotely

I bought a Mac mini 2018 (used). I checked the device, at the time of purchase the system was clean and did not contain any data of the previous owner, logged out of iCloud.

Then, at home, I started to log in to iCloud using my account and it turned out that the previous owner had not completely disabled his account.

At this stage, I checked the serial number through the iCloud verification service and received the answer: FindMyMac: ON

I contacted him. At first, he could not remember his password, then he managed to reset the password and he logged in to the account through the iCloud website and disabled Find My Mac.

I checked the serial number again through the iCloud verification service and received the answer: FindMyMac: OFF

But when I try to log in, I still get a message that this Mac is still associated with his account.

He don't want to tell me the password. Is there any way to do it remotely?

I tried to reinstall macOS through recovery mode (cmd + R) - nothing changed!

What should I do? Will recovery via DFU + Configurator help me?